1. Field
Exemplary embodiments of the present invention relate to a method for fabricating a semiconductor device, and more particularly, to a method for forming a side contact in a semiconductor device.
2. Description of the Related Art
When a buried bitline (BBL) is used in a semiconductor device having a cell of a vertical transistor, two cells may be adjacent to one buried bitline. In order to drive one cell by one buried bitline, a one-side-contact (OSC) process for insulating one active region while forming a contact in another active region may be performed. Hereinafter, the ‘OSC process’ will be briefly referred to as a side contact process. In a cell of a vertical transistor using the side contact process, an active region includes a body separated/isolated by a trench and a pillar formed on the body. The buried bitline fills the trench between bodies and a word line (or a vertical gate) extends in the direction crossing the buried bitline and being adjacent to the sidewall of the pillar. A vertical direction channel is formed by the word line.
A part of one sidewall of the body (an active region) is exposed through the side contact process to form a connection between the active region and the buried bitline. Furthermore, a dopant is implanted or diffused into the exposed part of the sidewall of the body to form a junction for the active region and the buried bitline, and the buried bitline and the body are electrically connected to each other through the junction.
However, since the active region has a high aspect ratio, the degree of process difficulty for forming a side contact is high and it is difficult to ensure the side contact of uniform position and height.